Method of repairing a cylinder head having cooling water passages

ABSTRACT

A method of repairing a cylinder head of a water cooled internal combustion engine that has damage to the boundary wall between a cooling water passage and the combustion chamber. According to the method, the boundary wall B located between a cooling water passage and a combustion chamber and including a crack is cut away from a cylinder head until the cut reaches a depth of one half the cross section of the cooling water passage. Then, a half-pipe portion, having a semicircular cross section that is equal in size to one-half the cross section of the cooling water passage is fixed in the cylinder head from which the boundary wall B has been removed such that an inner surface of the half-pipe may serve to form a cooling water passage after repair. With the use of the above method, the repair operation is completed easily with a low cost because the boundary wall B has only to be cut away to a shallow depth. Further, the use of a half-pipe portion, together with the remainder of the original cooling water passage ensures that the cooling water passage will be restored to its original state.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of repairing a cylinderhead of a water cooling type internal combustion engine, in particular,to a method of repairing a broken portion within the cylinder headlocated between a cooling water passage and the combustion chamber.

[0003] 2. Description of the Related Art

[0004] A water cooling type internal combustion engine usually hascooling water passages formed within a cylinder head which defines initself a combustion chamber for the engine. It has been found thatcracks, other damage and even broken portions within the cylinder headbetween the cooling water passage and the combustion chamber will occurafter a long-period use of such internal combustion engine.

[0005] It is desirable to repair, rather than replace, damaged or brokenportions. However, to make repair of the broken portions of a cylinderhead of an internal combustion engine a viable option, it is requiredthat the repairing process be accomplished easily, at a low cost andthat a damaged cylinder head be restored to its original state andprovide its predetermined performance after repairing.

[0006] It is an object of the present invention to provide a novel anduseful method of repairing a cylinder head of an internal combustionengine, so as to satisfy and meet the above requirements.

SUMMARY OF THE INVENTION

[0007] To achieve the above-described object of the present invention,the present invention provides an improved method for repairing acylinder head of an internal combustion engine. The method comprises thesteps of: cutting away the boundary walls including broken portions,preferably until the cut reaches a depth of one-half the cross sectionof the cooling water passage; fixing pipe portions, preferablyhalf-pipes each having a semicircular cross section which is equal insize to one-half the cross section of the cooling water passage, in thecylinder head from which the boundary walls have been partially removedin a manner such that an inner surface of a half-pipe portion may serveto form a cooling water passage after repairing treatment.

[0008] By virtue of the method according to the present invention, therepair operation can be completed easily at a low cost because thecylinder head need only be cut away to a shallow depth. Further, atleast a part of a cooling water passage is formed by the inner surfaceof a half-pipe having a semicircular cross section that is equal in sizeto one-half the cross section of the cooling water passage. As a result,the remaining portion of the original passage serves as a guide toensure that the cooling water passage is restored to its original state.In this way engine performance is maintained.

[0009] In accordance with a preferred embodiment, prior to the step offixing a half-pipe in a predetermined position, a guide member having anouter periphery surface that conforms to the corresponding cooling waterpassage without forming any clearance therebetween, is inserted in thecooling water passage to be repaired. In this way, the outer peripherysurface of a guide member may serve as a positioning member forpositioning a pipe portion so that the half-pipe may be attached at acorrect position with precision. This step ensures easy attachment ofeach of the half-pipe portions. Moreover, when a half-pipe is beingfixed in position by means of welding, the outer periphery surface of aguide member can serve to prevent molten metal from entering a coolingwater passage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a cross sectional view of a part of a water cooling typeinternal combustion engine containing a cylinder head suitable to berepaired by the method according to one embodiment of the presentinvention.

[0011]FIG. 2 is an enlarged sectional view indicating an essential partof the cylinder head of FIG. 1.

[0012]FIG. 3 is a top plane view indicating the cylinder head of FIG. 1,when viewed from the combustion chamber.

[0013]FIG. 4 is a side view indicating a half-pipe.

[0014]FIG. 5 is a front view of the half-pipe.

[0015]FIG. 6 is an explanatory view indicating one step of the methodaccording to one embodiment of the present invention.

[0016]FIG. 7 is an explanatory view indicating one step of the methodaccording to one embodiment of the present invention.

[0017]FIG. 8 is an explanatory view indicating one step of the methodaccording to one embodiment of the present invention.

[0018]FIG. 9 is a cross sectional view indicating a part of a cylinderhead repaired by the method according to one embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring to FIG. 1, a water cooling type internal combustionengine includes a cylinder 1, a cylinder head 2 secured on the cylinder1, a piston 4 capable of reciprocating within the cylinder 1, acombustion chamber 3 defined by the cylinder 1 and the cylinder head 2and the piston 4, an intake port 5 for intaking a mixed gas into thecombustion chamber 3, and an exhaust port 6 for exhausting burned gasfrom the combustion chamber 3. The exhaust port 6 extends through thecentral portion of the cylinder head 2.

[0020] The cylinder head 2 contains a plurality of cooling fluidpassages (cooling water passages) 7 each having a circular cross sectionand having an opening 7 a on the outer surface of the cylinder head 2.FIG. 3 is a top plane view indicating the cylinder head of FIG. 1, whenviewed from the combustion chamber 3. As can be clearly seen from FIG.3, the plurality of cooling water passages 7 are arranged to extendradially within the cylinder head 2. In this manner, the cooling fluid(the cooling water) flowing through these cooling water passages 7 coolsthe cylinder head 2. In one embodiment, the cooling water passages 7 areformed by boring in the direction shown by an arrow A in FIG. 1 from theouter surface of the cylinder head 2 prior to the assembling of theentire engine.

[0021] Referring to FIG. 2, in the cylinder head 2, it has been foundthat a boundary wall B, located between a cooling water passage 7 andthe combustion chamber 3, is likely to be broken after a long period useof the internal combustion engine. The most frequently occurringphenomenon is a crack 12. In accordance with the present embodiment, acylinder head 2 (see FIG. 3) having a plurality of cracks 12corresponding to the plurality of cooling water passages 7 may berepaired according to a method that will be described in detail below.

[0022] To begin with, a damaged cylinder head 2 is removed from thecylinder 1. Then, as shown in FIG. 2, a boundary wall B including acrack 12 is cut down to a half depth of the cross section of a coolingwater passage 7, with the use of a cutting machine such as a workinglathe. Further, in the present embodiment, as shown in FIG. 2, an arearepresented by a broken line is about to be removed. Moreover, accordingto the present embodiment, when a plurality of cracks 12 are to berepaired at the same time, an annular portion between a circle C1 and acircle C2 is removed therefrom, as shown in FIG. 3. Once this annularportion is removed, an annular groove 13 continuously connected with thecooling water passage surfaces 7 b (see FIG. 9) each having asemicircular cross section, is formed on the inner surface 2 a of thecombustion chamber 3 within the cylinder head 2.

[0023] Second, preferably, as shown in FIG. 2, a guide member 9 isinserted from the opening 7 a of the cooling water passage 7 inwardly tothe interior of the cooling water passage 7. This guide member 9, asshown in FIGS. 6-9, has an outer periphery surface 9 a conformable withthe cooling water passage 7 without forming any clearance.

[0024] Such guide member 9 is made of copper or brass. Preferably, theguide member 9 is formed of a material which is capable of preventing amolten metal such as a filler metal or base metal from adhering to thesurface thereof. Further, the guide member 9 may be made of either asolid rod or a hollow pipe. With the guide member 9 inserted in thecooling water passage 7, as shown in FIG. 6, the outer periphery surface9 a of the guide member 9 will be exposed in the groove 13.

[0025] Afterwards, each of the cooling water passages 7 is treated inthe following manner. Namely, as shown in FIG. 8, a half-pipe 8 shown inFIGS. 4 and 5 is fixed within the groove 13 of the cylinder head 2 bymeans of welding such as TIG (Tungsten Inert Gas) arc welding, MIG(Metallic Inert Gas) arc welding or submerged arc welding, with the useof a filler metal 10. Under this condition, it is preferable that thewelding operation be performed after welding portions have beenpreheated to a temperature of 100-150° C. with the use of a gas burner.

[0026] Each half-pipe 8, upon being fixed in position as shown in FIG.9, has a semicircular cross section which is as large as the half of thecross section of a cooling water passage 7. Therefore, as shown in FIG.5, the inner surface 8 a of each half-pipe 8 is the same as the half ofa cooling water passage 7. Further, each half-pipe 8, as shown in FIG.6, has a length which is equal to the width W (see FIG. 3) of a groove13. In this way, as shown in FIG. 6, a half-pipe 8 is mounted on theguide member 9 so as to cover up the outer surface 9 a of the guidemember 9, which was previously exposed in the groove 13. At this time,as shown in FIG. 9, the inner surface 8 a of the half-pipe 8, togetherwith the inner surface 7 b of the cooling water passage 7 having asemicircular cross section, serve to define a cooling water passage 7upon completion of the repairing of the engine.

[0027] In this way, with the use of the guide member 9, it is sure thatthe half-pipe 8 may be attached in position with a great ease and thatsuch attachment will be accomplished with an improved accuracy.

[0028] Further, after the half-pipe 8 is welded into the cylinder head2, the outer surface 9 a of the guide member 9 may serve to preventmolten metal from invading into the cooling water passage 7. Since theguide member 9 is made of a copper or a brass, a material capable ofpreventing adhesion of molten metal to the surface thereof, the guidemember 9 can be easily pulled out of the cylinder head 2.

[0029] Referring again to FIGS. 4 and 5, in order to obtain a higherwelding strength, each half-pipe 8 is preferred to be chamfered so thateach end in its longitudinal direction is formed with a chamfer 8 b andthat each edge portion in its lateral direction has a chamfer 8 c.

[0030] Preferably, the half-pipe 8 is made of the same metal material asthe cylinder head 2. Alternatively, the half-pipe 8 is made of a metalmaterial which has the same thermal expansion coefficient as thematerial for forming the cylinder head 2. More preferably, eachhalf-pipe 8 may be made of a metal material having a higher durabilitythan the material of the cylinder head 2.

[0031] After each half-pipe 8 has been attached to the cylinder head 2,the guide member 9 is pulled so as to be removed from the cooling waterpassage 7, and, as shown in FIG. 9, the groove 13 is filled with fillermetal 11. In order to remove a welding stress, it is preferred toperform a shot peening, for example, on the surface of a first and asecond layer of the filler metal.

[0032] Subsequently, the cylinder head 2 as a whole is introduced intoan annealing furnace so as to receive an annealing treatment. Then, afinal finishing treatment is performed to grind the surface of thefiller metal 11 with the use of a grinding device such as a grinder,thereby rendering the inner surface 2 a of the cylinder head 2 to berestored to its original state.

[0033] With the use of the method according to the present embodiment,the cylinder head 2 has only to be cut off at a shallow depth, therebyrendering the repairing operation to be completed easily with a lowcost. Further, since each of the cooling water passages is repaired tobe restored to its original state, there would be no any unfavorablechanges brought to the cooling effect which should be provided by thecooling water passages.

What is claimed is:
 1. In a fluid cooled internal combustion engine ofthe type that includes a combustion chamber, cooling fluid passageshaving a circular cross section and a cylinder head that defines part ofthe combustion chamber and includes boundary walls located between thecombustion chamber and the cooling fluid passages, a method forrepairing damaged portions of the boundary walls located between thecombustion chamber and at least one of the cooling fluid passages, themethod comprising the steps of: cutting away the boundary walls of thecylinder head including the damaged portions until the cutting reaches adepth of one-half the cross section of the cooling fluid passage so thatthere is a remaining portion of the cooling fluid passage; fixing ahalf-pipe that has a semicircular cross section that is equal in size toone-half the cross section of the cooling fluid passage to the cylinderhead so that an inner surface of each half-pipe may serve to form,together with the remaining portion of the cooling fluid passage, acooling fluid passage.
 2. The method for repairing damaged portions ofthe boundary walls located between the combustion chamber and at leastone of the cooling fluid passages according to claim 1 , wherein beforethe step of fixing the half-pipe, a guide member, which has an outerperiphery surface that conforms with the cooling fluid passage withoutforming any clearance therebetween, is inserted in the cooling fluidpassage to form a guide for the half-pipe.
 3. The method for repairingdamaged portions of the boundary walls located between the combustionchamber and at least one of the cooling fluid passages according toclaim 2 , wherein the outer periphery surface of each guide member isformed of a metal material that is capable of preventing adhesion of amolten metal to said surface.
 4. The method for repairing damagedportions of the boundary walls located between the combustion chamberand at least one of the cooling fluid passages according to claim 2 ,wherein the outer periphery surface of each guide member is formed ofcopper or a brass.
 5. The method for repairing damaged portions of theboundary walls located between the combustion chamber and at least oneof the cooling fluid passages according to claim 1 , wherein eachhalf-pipe is fixed to the cylinder head by means of welding and whereineach half-pipe is formed with chamfer portions on its end and edgeareas.
 6. The method for repairing damaged portions of the boundarywalls located between the combustion chamber and at least one of thecooling fluid passages according to claim 1 , wherein each half-pipe isfixed to the cylinder head by means of welding adjacent portions of thehalf-pipe and cylinder head and wherein the portions to be welded arepreheated prior to the step of welding the half-pipe in the cylinderhead.
 7. The method for repairing damaged portions of the boundary wallslocated between the combustion chamber and at least one of the coolingfluid passages according to claim 6 , wherein the portions to be weldedare preheated to a temperature of 100-150° C.
 8. The method forrepairing damaged portions of the boundary walls located between thecombustion chamber and at least one of the cooling fluid passagesaccording to claim 1 , wherein the half-pipe is formed of the samematerial as the cylinder head.
 9. The method for repairing damagedportions of the boundary walls located between the combustion chamberand at least one of the cooling fluid passages according to claim 1 ,wherein the material forming the cylinder head has a predeterminedthermal expansion coefficient and durability and the half-pipe is madeof a metal material that has the same thermal expansion coefficient asthe material forming the cylinder head, and has a higher durability thanthe material forming the cylinder head.
 10. In a water cooled internalcombustion engine of the type that includes a combustion chamber,cooling fluid passages and a cylinder head that defines part of thecombustion chamber and includes boundary walls located between thecombustion chamber and the cooling fluid passages, a method forrepairing damaged portions of the boundary walls located between thecombustion chamber and at least one of the cooling fluid passages, themethod comprising the steps of: cutting away the boundary walls of thecylinder head including the damaged portions so that there is aremaining portion of the cooling fluid passage; fixing a pipe portion tothe cylinder head so that an inner surface of each pipe portion mayserve to form, together with the remaining portion of the cooling fluidpassage, a cooling fluid passage.
 11. The method for repairing damagedportions of the boundary walls located between the combustion chamberand at least one of the cooling fluid passages according to claim 10 ,wherein before the step of fixing the pipe portion, a guide member,which has an outer periphery surface that conforms with the coolingfluid passage without forming any clearance therebetween, is inserted inthe cooling fluid passage to form a guide for the pipe portion.
 12. Themethod for repairing damaged portions of the boundary walls locatedbetween the combustion chamber and at least one of the cooling fluidpassages according to claim 11 , wherein the outer periphery surface ofeach guide member is formed of a metal material that is capable ofpreventing adhesion of a molten metal to said surface.
 13. The methodfor repairing damaged portions of the boundary walls located between thecombustion chamber and at least one of the cooling fluid passagesaccording to claim 11 , wherein the outer periphery surface of eachguide member is formed of copper or a brass.
 14. The method forrepairing damaged portions of the boundary walls located between thecombustion chamber and at least one of the cooling fluid passagesaccording to claim 10 , wherein each pipe portion is fixed to thecylinder head by means of welding and wherein each pipe portion isformed with chamfer portions on its end and edge areas.
 15. A cylinderhead that defines at least part of a combustion chamber in a fluidcooling type internal combustion engine that has cooling fluid passagesseparated from the combustion chamber by boundary walls, wherein atleast a part of a cooling fluid passage is formed by a pipe portionhaving an inner surface that together with a portion of the boundarywall forms the cooling fluid passage.
 16. The cylinder head of claim 15, wherein the pipe portion is a half pipe that has a semicircular crosssection which is equal in size to a half cross section of the coolingfluid passage.
 17. A fluid cooled internal combustion engine that has acombustion chamber, a cylinder head and cooling fluid passages separatedfrom the combustion chamber by boundary wall portions of the cylinderhead, wherein at least a part of a cooling fluid passage is formed by apipe portion having an inner surface that together with a portion of theboundary wall forms the cooling fluid passage.
 18. The fluid cooledinternal combustion engine of claim 17 , wherein the pipe portion is ahalf pipe that has a semicircular cross section which is equal in sizeto a half cross section of the cooling fluid passage.